Work Vehicle having Engine and Belt-Type Continuously Variable Transmission Device

ABSTRACT

A work vehicle includes: a muffler which flows exhaust from an engine and extends in a transverse direction so as to allow the exhaust from the engine to flow in the transverse direction; and a CVT case for covering a belt-type CVT positioned frontward of the muffler in a longitudinal direction. The CVT case includes a cooling structure for introducing cooling air from outside, cooling the belt-type CVT, and discharging the cooling air from a discharge part. An exhaust duct includes an inflow opening to be connected to the discharge part for allowing the cooling air to flow into the exhaust duct, and an exhaust opening for allowing the cooling air to flow out rearward. The exhaust opening is elongated in an extending direction of the muffler and oriented in a direction that allows the cooling air flowing out to hit the muffler.

BACKGROUND

1. Field of the Invention

The present invention relates to a cooling technique of a belt-typecontinuously variable transmission device (CVT) and a muffler in a workvehicle having an engine and the belt-type CVT.

2. Description of the Related Art

With respect to the cooling technique of the belt-type CVT, JapaneseUnexamined Patent Application Publication No. 2005-238988 describes avehicle in which a body frame is provided with an engine, a belt-typeCVT for changing a driving force of the engine, and a muffler connectedto an exhaust pipe of the engine. In this patent document, the belt-typeCVT has a transmission cooling system for sucking external cooling airfrom a feed duct; supplying the cooling air into a belt case to therebycool the belt-type CVT; and sending this cooling air from the belt casethrough an exhaust duct to a rear part of a vehicle body. The exhaustduct and the muffler are arranged in parallel with each other in alateral direction, and a discharge direction of a discharge port at arear end of the exhaust duct is oriented to the muffler, to thereby leadthe cooling air discharged from the discharge port to the muffler and tocool the muffler.

However, in a case where the discharge port at the rear end of theexhaust duct is oriented in the lateral direction of the vehicle body,when the vehicle body is running, an air flow from outside acts on thecooling air discharged from the discharge port. When the air flow fromoutside acts on the cooling air discharged from the discharge port, aposition on the muffler on which the cooling air is blown is displacedrearward of the vehicle body and the cooling air discharged from thedischarge port is diffused by the air flow from outside. As a result, anamount of the cooling air led to a surface of the muffler is reduced,and thus cooling performance is lowered.

Similar to the above-described prior art, Japanese Unexamined PatentApplication Publication No. 2006-27425 describes a transmission coolingsystem for sucking the external cooling air from an intake duct;supplying the cooling air into the belt case to thereby cool thebelt-type CVT; and sending this cooling air from the belt case through adischarge duct to the rear part of the vehicle body. The muffler and thedischarge duct are parallelly arranged closer to each other. In thiscase, by positioning the muffler (object to be cooled) closer to thedischarge duct (cooling means), an area around the muffler iseffectively cooled.

However, even though the lowering in the cooling performance by the airflow from outside during the vehicle body running is suppressed, thecooling itself is not so efficient.

SUMMARY OF THE INVENTION

In view of the above, it is desirable to provide a work vehicle in whichtemperature raise of the muffler is suppressed by utilizing the coolingair which has been used for cooling the belt-type CVT.

The work vehicle according to the present invention having an engine anda belt-type CVT, includes: a muffler which is configured to flow exhaustfrom the engine and extends in a transverse direction of a vehicle bodyso as to allow the exhaust from the engine to flow in the transversedirection of the vehicle body; a CVT case which is configured to coverthe belt-type CVT and positioned forward of the muffler in alongitudinal direction of the vehicle body; and an exhaust ductincluding an inflow opening to be connected to a discharge part of theCVT case for allowing cooling air to flow into the exhaust duct and anexhaust opening for allowing the cooling air to flow out rearward of thevehicle body. The CVT case includes a cooling structure configured tointroduce the cooling air from outside, cool the belt-type CVT, anddischarge the cooling air from the discharge part. The exhaust openingof the exhaust duct is elongated in an extending direction of themuffler and oriented in a direction that allows the cooling air flowingout to hit the muffler. A cross-sectional horizontal length of theexhaust opening in the extending direction of the muffler is longer thana cross-sectional horizontal length of the inflow opening, and across-sectional vertical length of the exhaust opening is shorter than across-sectional vertical length of the inflow opening.

According to this configuration, the cooling air which has been used forcooling an inside of the CVT case is discharged from the discharge partof the CVT case through the exhaust duct to a rear side of the vehiclebody, and blown to the muffler in a direction orthogonal to an extendingdirection of the muffler (longitudinal direction of the muffler). Inother words, the cooling air hits directly into the muffler.Accordingly, when the vehicle body is running, the cooling airdischarged from the discharge part reaches the surface of the mufflerwithout being influenced by the air flow from outside, and thus thecooling of the muffler is achieved. In addition, since a cross sectionof the exhaust opening for exhausting the cooling air is formed so as tocorrespond to the muffler in the extending direction, a hitting degreeon the muffler by the cooling air is high, and the hitting is efficient.As a result, temperature raise of the muffler is effectively suppressedby utilizing the cooling air which has been used for cooling thebelt-type CVT.

It is convenient when a heat shield plate is arranged along an outerface of the muffler at a distance, and the cooling air discharged fromthe exhaust duct is supplied to a space between the muffler and the heatshield plate. With this configuration, by supplying the cooling air fromthe exhaust duct to the space between the outer face of the muffler andthe heat shield plate, the cooling is realized in which the cooling airis continuously brought into contact with the outer face of the muffler.In other words, as compared with a local cooling in which the coolingair is simply blown to an object, a wider area of the outer face of themuffler can be efficiently cooled.

By setting the cross-sectional horizontal length of the exhaust openingto approximately twice the cross-sectional horizontal length of theinflow opening, a wider area of the outer face of the muffler can becooled.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a work vehicle.

FIG. 2 is a plan view showing a configuration of transmission of thework vehicle.

FIG. 3 is a perspective view showing a configuration of frame.

FIG. 4 is a side view showing a configuration of suspension of rearwheels.

FIG. 5 is a side view showing arrangement of an engine, a belt-type CVT,and the like.

FIG. 6 is a perspective view showing the arrangement of the engine, thebelt-type CVT, and the like.

FIG. 7 is a plan view showing the arrangement of the engine, thebelt-type CVT, and the like.

FIG. 8 is a planar diagram showing a cooling air flow in the belt-typeCVT.

FIG. 9 is a side diagram showing the cooling air flow in the belt-typeCVT.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinbelow, embodiments of the present invention will be described indetail with reference to the accompanying drawings.

(Overall Configuration)

As shown in FIGS. 1 and 2, a work vehicle includes: a pair of freelysteerable right and left front wheels 1 and a pair of right and leftrear wheels 2 provided in a vehicle body 3; a driving part 10 disposedin a middle part of the vehicle body 3; a truck box 4 disposed in a rearpart of the vehicle body 3; and a motor part 30 disposed below the truckbox 4.

This work vehicle is configured as a four-wheel-drive type in which adriving force is transmitted from the motor part 30 to the front wheels1 and the rear wheels 2, and is used for multipurpose work, includingagricultural work and transportation work. At a position surrounding thedriving part 10, a protection frame 11 for protecting the driving part10 is provided.

The truck box 4 has a function of dump-wise discharging a load byraising a front end side of the truck box 4, and a rear end of the truckbox is swingably supported by the vehicle body 3 about an axis. Inaddition, an actuator (not shown) of a hydraulic type is provided whichis for raising and lowering the front end side of the truck box 4.

The driving part 10 includes: a driver's seat 12 on which a driver is tobe seated; a steering wheel 13 for controlling steering of the frontwheels 1; a shift lever 14; an accelerator pedal 15 for controlling arunning speed; and a brake pedal 16 for operating braking devices 17 ofthe front wheels 1 and the rear wheels 2. A passenger seat is providednext to the driver's seat 12, and the driving part 10 is provided with abench seat formed of a single seat base and a single seat back bothelongated in a transverse direction of the vehicle body.

The shift lever 14 is configured to set the running speed and switchbetween a forward movement and a backward movement by a single leveroperation. Alternatively, for example, the driving part 10 may beprovided with two levers, including a lever for gear change and aforward-reverse lever for switching between the forward movement and thebackward movement.

As shown in FIG. 3, a body frame forming the vehicle body 3 has: a pairof right and left main frames 21 extending below the driving part 10 ina front-rear direction from a front end of the vehicle body to the motorpart 30; and a plurality of cross-frames 22 connecting the right andleft main frames 21. The protection frame 11 is formed of: a pair ofright and left side frames 11A; and a plurality of transversal frames11B connecting the right and left side frames 11A. The protection frame11 is connected to a pair of the right and left main frames 21 throughan intermediate frame and the like.

Each of the right and left side frames 11A is formed in a loop shape anda step 23 made of a plate is provided at a position where lower endparts of the side frames 11A and a pair of the right and left mainframes 21 are connected. In addition, a back plate 24 bridging a spacebetween the right and left side frames 11A is provided rearward of thedriver's seat 12. The step 23 serves a boarding area for the driver, andthe back plate 24 supports the seat back of the driver's seat 12.

As shown in FIGS. 2 and 4-7, the motor part 30 includes: an engine 31 ofan air-cooling type; a dry- and belt-type continuously variabletransmission device (CVT) 32; and a transmission. The transmissionincludes a transmission case 33 in which a gear shift mechanism (notshown) and a differential mechanism (not shown) are installed. In alower end part of the transmission case 33, there are provided a pair ofright and left rear wheel drive shafts 34 for transmitting the drivingforce from the differential mechanism to the rear wheels 2, and rearaxle cases 35 encasing the respective rear wheel drive shafts 34.

From the lower end part of the transmission case 33, a power take-offshaft 36 extends frontward. In a lower part of the vehicle body 3, anintermediate shaft 37 for transmitting the driving force from the powertake-off shaft 36 is provided, and the driving force is transmitted fromthe intermediate shaft 37 to a differential case 38 in a front part ofthe vehicle body 3 in which a front wheel drive shaft 39 fortransmitting the driving force from the differential case 38 to thefront wheels 1 is provided.

A universal coupling, such as Cardan joint, is disposed between thepower take-off shaft 36 of the transmission and the intermediate shaft37, and likewise, another universal coupling is disposed between thefront and rear intermediate shafts 37, and still another universalcoupling is disposed between the intermediate shaft 37 and an inputshaft of the differential case 38. In addition, a universal coupling,such as Cardan joint, is disposed between an output shaft of thedifferential case 38 and the front wheel drive shaft 39, and likewise,another universal coupling is disposed between the front wheel driveshaft 39 and a shaft of the front wheel 1.

Though not shown, in the transmission case 33, a clutch mechanism isencased which is switchable between a transmitting state in which thedriving force is transmitted to the power take-off shaft 36 and acut-off state in which the driving force is cut off. The clutchmechanism is switchable through an operation by the driver, and bysetting the clutch mechanism to the transmitting state, afour-wheel-drive state is obtained in which the rear wheels 2 and thefront wheels 1 are driven at the same time, and by setting the clutchmechanism to the cut-off state, a two-wheel-drive state is obtained inwhich only the rear wheels 2 are driven.

It should be noted that the braking device 17 is provided on each ofaxle ends of a pair of the right and left front wheel drive shafts 39and each of axle ends of a pair of the right and left rear wheel driveshafts 34. The braking devices 17 function in such a manner that thebraking force acts on the front wheels 1 and the rear wheels 2 by anoperation of the brake pedal 16.

The gear shift mechanism (not shown) of the transmission is operated bythe shift lever 14. The gear shift mechanism is configured to change therunning speed of the vehicle body 3 and switch running directions(between the forward movement and the backward movement) in accordancewith the operation of the shift lever 14.

(Suspension)

The right and left front wheels 1 are mounted on the body frame byindependent front suspension of a strut type. In other words, in each ofthe front wheels 1, a base end side of a lower arm (not shown) isswingably supported by the body frame, and an axle of the front wheel 1is supported by a swingable end portion of the lower arm. Between thelower arm and the body frame, a suspension unit 25 (see FIG. 1) formedof a coil spring and a shock absorber is provided. With thisconfiguration, the front wheels 1 are mounted on the vehicle body.

With this suspension, the right and left front wheels 1 areindependently movable in a vertical direction in accordance withroughness of a road surface, and when a vertical movement involves ashock, the shock is absorbed by the suspension unit 25.

As shown in FIGS. 1, 4 and 5, the right and left rear wheels 2 aremounted on the body frame by rigid axle suspension. In other words, theright and left main frames 21 are provided with a pair of right and leftauxiliary frames 26. The rear axle cases 35 is supported by therespective auxiliary frames 26, and between the rear axle cases 35 andthe body frame, the respective suspension units 25 each formed of thecoil spring and the shock absorber are provided. With thisconfiguration, the rear wheels 2 are mounted in the vehicle body.

A pair of the right and left auxiliary frames 26 includes: a pair ofright and left side members 26A each bent in a L-shape; lower arms 26Bswingably connecting respective front ends of a pair of the right andleft side members 26A and the main frame 21; and upper arms 26Cswingably connecting respective upper ends of a pair of the right andleft side members 26A and the main frame 21. A pair of the right andleft side members 26A are connected through a connection frame 28 whichsupports a bottom part of the engine 31 in a connected state.

Specifically, a front end of the lower arm 26B is swingably connected toa bracket 21A on a lower face of an intermediate part of the main frame21 through a rubber bush. A rear end of the lower arm 26B is swingablyconnected to a bracket 26L at the front end of the side member 26Athrough a rubber bush. In addition, a front end of the upper arm 26C isswingably connected to a bracket 21B on a lower face of a rear part ofthe main frame 21 through a rubber bush. A rear end of the upper arm 26Cis swingably connected to a bracket 26H at a rear end of the side member26A. Further, the right and left side members 26A are supported on themain frame 21 through a lateral rod 27.

The rear axle case 35 is connected to an upper face of the right (left)side member 26A by a holder 26E to which a lower end part of thesuspension unit 25 is connected. In addition, the bottom part of theengine 31 is supported on the connection frame 28 connecting the rightand left side members 26A, as described above. With this configuration,the engine 31 and the transmission case 33 are supported by the rightand left side members 26A.

Accordingly, when the right and left rear wheels 2 moves vertically inaccordance with the roughness of the road surface, the transmission, theengine 31 and the belt-type CVT 32 integrally move in the verticaldirection along with the vertical movement of the rear axle case 35.When the vertical movement involves a shock, the shock is absorbed bythe suspension unit 25.

(Motor Part)

As shown in FIGS. 4-8, in the motor part 30, the engine 31 is arrangedin such a manner that a crankshaft 31C (see FIG. 8) is transversallyoriented, and rearward of and next to the engine 31, the transmissioncase 33 is arranged in such a manner that an input shaft 33A istransversally oriented. Rearward of the transmission case 33, a muffler40 transversally extending is disposed, and the belt-type CVT 32 isdisposed on a lateral side of both the engine 31 and the transmissioncase 33. The muffler 40 is in a shape of a column whose axis istransversally oriented and whose lower end part is fixed to a bracketextended from the auxiliary frame 26.

The engine 31 is configured in such a manner that a cylinder head 31B isconnected to a cylinder block 31A by which the crankshaft 31C issupported. The cylinder head 31B is connected to the cylinder block 31Aso that the cylinder head 31B is positioned obliquely above andfrontward of the cylinder block 31A. Accordingly, a difference in aheight level between an upper face of the cylinder block 31A and thecylinder head 31B is suppressed small, so as to make a size of theentire engine in the vertical direction compact.

Since the engine 31 and the transmission case 33 are arranged next toeach other in the front-rear direction, a space 30A is formed between anupper part of the engine 31 (upper part of the cylinder block 31A) andan upper part of the transmission case 33. A pair of right and leftconnecting projections 31D protrude obliquely upward and rearward fromthe upper face of the cylinder block 31A, and a pair of right and leftconnecting projections 33D protrude upward from an upper face of thetransmission case 33. A flat connecting plate 41 is horizontallydisposed above and away from an upper face of the engine 31 and theupper face of the transmission case 33 at a position above the space30A, and a front end part of the connecting plate 41 is connected tohorizontal parts on a rear end side of the connecting projection 31Dwith bolts 41A, while a rear end part of the connecting plate 41 isconnected to horizontal parts of an upper end of the connectingprojection 33D with the bolts 41A. The connecting plate 41 is folded ina shape of a reversed shallow V seen from a side (in a mountain fold),and has a cover part that defines a space therebelow. Reinforcing ribs41C protruding upward and extending in the front-rear direction areformed in an upper face of the cover part, and in a rear part of theconnecting plate 41, a cutout 41D is formed which allows access to anopening 33E for maintenance of the transmission case 33.

The connecting plate 41 is arranged so that the cover part is disposednearly horizontally, and therefore, even when a tensile force in anendless belt 63 of the belt-type CVT 32 is exerted between an outputshaft 65A of the engine 31 and the input shaft 33A of the transmission,the connecting plate 41 prevents a displacement in relative positionbetween the engine 31 and the transmission case 33. In other words, theoutput shaft 65A of the engine 31 and the input shaft 33A of thetransmission are retained at approximately the same height level whilethey are transversally oriented. Accordingly, a width direction of theconnecting plate 41 nearly coincides with an axial direction of theoutput shaft 65A and an axial direction of the input shaft 33A.

As shown in FIG. 8, in the belt-type CVT 32, the output shaft 65A isprovided with a driving pulley 61, the input shaft 33A is provided witha driven pulley 62, and the endless belt 63 is wound around the pulleys61,62. Since the width direction of the connecting plate 41 nearlycoincides with the axial direction of the output shaft 65A and the axialdirection of the input shaft 33A as described above, the tensile forcein the endless belt 63 is exerted in a direction that makes outer endsides of the axes move closer, and the connecting plate 41 with alateral width receives this tensile force. Therefore, with the presenceof the connecting plate 41, the displacement in the relative positionbetween the engine 31 and the transmission case 33 can be prevented.

The connecting plate 41 may be inclined more or less relative to theaxis of the output shaft 65A and the axis of the input shaft 33A, aslong as the connecting plate 41 is in a posture in which the widthdirection of the connecting plate 41 can receive the force that is aptto change a positional relationship between the output shaft 65A and theinput shaft 33A into a nonparallel state. It should be noted that, aswill be described later, the output shaft 65A of the engine 31 serves asthe output shaft 65A of a centrifugal clutch 65 to which the drivingforce is transmitted from the engine 31, and alternatively, thecentrifugal clutch 65 may be omitted and the crankshaft 31C of theengine 31 may be extended into a CVT case 64 and serve as output shaft,on which the driving pulley 61 is provided.

In the space 30A, a generator 42 and a starter motor 43 as electriccomponent are disposed, and above these components, the connecting plate41 is disposed. With this configuration, when the work vehicle is washedor it rains hard, the connecting plate 41 prevents water from enteringthe generator 42 and the starter motor 43. It should be noted that theelectric component to be disposed in the space 30A is not limited to thegenerator 42 and the starter motor 43, and examples include fuse andelectrical wiring for engine.

When the work vehicle is assembled, the engine 31 and the transmissioncase 33 are connected through the connecting plate 41, and then thebelt-type CVT 32 is further connected thereto, to thereby prepare aunified body, which is then mounted on the vehicle body. Whenmaintenance of the work vehicle is performed, the unified body isremoved from the vehicle body. In order to facilitate such operations,the connecting plate 41 may have a mount part 41B for a hoisting tool(not shown) for hoisting the unified body. In one example, the mountpart 41B is a screw hole formed in the connecting plate 41, and thehoisting tool is supported through threadable engagement with the screwhole. It should be noted that a simple through hole may be provided asthe mount part 41B. In this case, a connection structure may be those inwhich a bolt portion is inserted into the through hole and the hoistingtool and then threadably engaged with a nut to thereby connect and fixthe hoisting tool.

It should be noted that, when the unified body is hoisted, in order torealize a stable hoist, it is desirable that the hoisting tools areattached to a plurality of parts of the right and left rear axle cases35 so as to exert forces in the plurality of the hoisting tools forsuspension.

On the lateral side of the engine 31 opposite to the side where thebelt-type CVT 32 is disposed, an engine blower unit 50 is provided. Theengine blower unit 50 includes: a fan 50A rotatable by the driving forceof the engine 31; and a case 50B for encasing the fan 50A. In the case50B, there are formed an intake opening 50C and a bulging part 50Dbulging from a rear part of the case 50B to a side of the space 30A.

With this configuration, when the engine 31 is operated, along withrotation of the fan 50A, most of cooling air sucked from the intakeopening 50C of the case 50B is supplied from one end portion of the case50B to the cylinder block 31A and the cylinder head 31B. In addition,when the cooling air is supplied in this manner, a portion of thecooling air is sent from the bulging part 50D of the other end part ofthe case 50B through a cooling air passage 30R as shown in FIG. 7, tothe space 30A below the connecting plate 41. The cooling air suppliedfrom the cooling air passage 30R to the space 30A cools the generator 42and the starter motor 43 as electric components disposed in the space30A.

As shown in FIGS. 1 and 7, on a back side of the back plate 24, a firstair cleaner 45 for intake air of the engine 31 and a second air cleaner46 for intake cooling air of the belt-type CVT 32 are disposed in aspace between the driving part 10 and the truck box 4.

To the cylinder head 31B of the engine 31 is connected to an air-intakepipe 47 whose distal end is connected to the first air cleaner 45. Tothe cylinder head 31B is connected to an exhaust pipe 48 whose terminalis connected to the muffler 40. The muffler 40 has a cylindricalstructure, and is disposed rearward of the transmission case 33 in aposture that a longitudinal direction of the muffler 40 is oriented inthe transverse direction of the vehicle body. A heat shield plate 49made of metal, such as steel plate, is provided so as to surround anupper face part of the muffler 40, and a gap is formed between the heatshield plate 49 and an outer face of the muffler 40. In addition, on thelateral side of the engine 31, the centrifugal clutch 65 is disposed,and an intake part 51 in the vicinity of the centrifugal clutch 65 isconnected to an intake duct 67 whose distal end is connected to thesecond air cleaner 46.

(Motor Part: Belt-Type CVT)

As shown in FIG. 8, in the belt-type CVT 32, the endless belt 63 made ofrubber is wound around both the driving pulley 61 whose belt windingdiameter is changeable and the driven pulley 62 whose belt windingdiameter is also changeable, and these are encased in the CVT case 64.It should be noted that a metal belt may be used as the endless belt 63.

The belt-type CVT 32 is provided with the centrifugal clutch 65 to whicha rotary driving force is transmitted from the crankshaft 31C of theengine 31, and the driving pulley 61 is provided on the output shaft 65Aof the centrifugal clutch 65. The driven pulley 62 is provided on theinput shaft 33A of the transmission. The output shaft 65A of thecentrifugal clutch 65 is arranged coaxially with the crankshaft 31C andserves as the output shaft 65A of the engine 31.

When a rotational speed of the crankshaft 31C is less than a set value,the centrifugal clutch 65 is in a cut-off state, and a turning force ofthe crankshaft 31C is not transmitted to the output shaft 65A. When therotational speed of the crankshaft 31C is above the set value, thecentrifugal clutch 65 is in a connecting state, and the turning force ofthe crankshaft 31C is transmitted to the output shaft 65A.

The driving pulley 61 includes a fixed sheave 61A disposed on a base endside (closer side to the engine 31) of the output shaft 65A and amovable sheave 61B disposed on a distal end side of the output shaft65A. In addition, on a protruding end of the output shaft 65A, a windingdiameter adjusting mechanism 66 for adjusting a position of the movablesheave 61B is provided.

The winding diameter adjusting mechanism 66 is configured to move themovable sheave 61B closer to the fixed sheave 61A so as to enlarge thebelt winding diameter of the driving pulley 61, as a rotational speed ofthe output shaft 65A becomes higher; and to the contrary, move themovable sheave 61B away from the fixed sheave 61A so as to reduce thebelt winding diameter of the driving pulley 61, as the rotational speedof the output shaft 65A becomes lower.

The driven pulley 62 includes a movable sheave 62A disposed on a baseend side (closer side to the transmission case 33) of the input shaft33A, a fixed sheave 62B disposed on a distal end side of the input shaft33A, and a coil spring 62C for exerting a biasing force in such a mannerthat the movable sheave 62A is biased to the fixed sheave 62B.

The coil spring 62C is configured to exert the biasing force forpositioning the movable sheave 62A of the driven pulley 62 in accordancewith a tensile force acting on the endless belt 63. In other words, whenthe belt winding diameter of the driving pulley 61 is changed, thetensile force acting on the endless belt 63 is changed. This mechanismrealizes an actuation in such a manner that, as the tensile forceincreases, the movable sheave 62A is moved away from the fixed sheave62B, and as the tensile force decreases, the movable sheave 62A is movedcloser to the fixed sheave 62B. Therefore, when the belt windingdiameter of the driving pulley 61 is small, the belt winding diameter ofthe driven pulley 62 is set to a large value, and to the contrary, whenthe belt winding diameter of the driving pulley 61 is large, the beltwinding diameter of the driven pulley 62 is set to a small value.

As shown in FIG. 8, the CVT case 64 includes: a case main body 64Asupported on a vehicle body side (by at least one of the transmissioncase 33 and the engine 31); and a cover member 64B removably supportedby the case main body 64A. Among wall faces of the case main body 64A, awall on an engine side has a cooling air inlet 64C formed therein, and awall on a transmission case 33 side has a bulging part 64D bulgingtowards a side opposite to the cover member 64B (transmission case 33side). On an outer periphery of the case main body 64A, a main flangeface 64E is formed. In the case main body 64A, on an engine side (frontside), a flat and vertical wall face 64W perpendicular to the outputshaft 65A is formed, and on an transmission side (rear part side), abulging wall 64X bulging from the vertical wall face 64W to thetransmission case 33 side is formed, which creates the bulging part 64D.With this configuration of the bulging part 64D, a large space is formedon the transmission side relative to the driven pulley 62.

As shown in FIG. 9, for a purpose of sending the cooling air rearward byutilizing a wind pressure generated by rotation of the driven pulley 62,a discharge part 64F is formed in the bulging part 64D, rearward of anupper part of an outer periphery of the driven pulley 62. The drivenpulley 62 is configured to rotate in a direction indicated with an arrowR in FIG. 9. The cooling air introduced to the CVT case 64 cools aninside of the CVT case 64, and moves in a direction toward the dischargepart 64F. With this configuration, when the cooling air is dischargedfrom the discharge part 64F, along with the rotation of the drivenpulley 62, the wind pressure in a direction toward the discharge part64F on a rear side of the vehicle body 3 on a nearly horizontal tangentline to an upper part of the driven pulley 62 acts on the cooling air,and by utilizing the wind pressure, the cooling air is efficientlydischarged from the discharge part 64F.

The cover member 64B has a dimension configured to accommodate thedriving pulley 61, the winding diameter adjusting mechanism 66 and thedriven pulley 62, and has a sub flange face 64G formed in an outerperiphery thereof. In the CVT case 64, the case main body 64A and thecover member 64B are connected with bolts or the like, while sandwichinga seal material, such as rubber, between the main flange face 64E andthe sub flange face 64G.

With this configuration, when the rotational speed of the engine 31exceeds the set value by an operation of the accelerator pedal 15, thecentrifugal clutch 65 transmits the driving force of the crankshaft 31Cto the output shaft 65A. Since the output shaft 65A rotates at a lowspeed in an initial stage of this force transmission, the windingdiameter adjusting mechanism 66 sets the belt winding diameter of thedriving pulley 61 to a small value, and in conjunction with this, setsthe belt winding diameter of the driven pulley 62 to a large value.Accordingly, the driving force of the engine 31 is transmitted at a lowspeed ratio to the input shaft 33A of the transmission case 33. When therotational speed of the engine 31 is raised, as the output shaft 65Arotates at a higher speed, the winding diameter adjusting mechanism 66sets the belt winding diameter of the driving pulley 61 to a largevalue, and in conjunction with this, sets the belt winding diameter ofthe driven pulley 62 to a small value. Accordingly, the driving force ofthe engine 31 is transmitted at a high speed ratio to the input shaft33A of the transmission case 33.

(Motor Part: Cooling Configuration of Belt-Type CVT)

A clutch case 52 surrounding the centrifugal clutch 65 is connected tothe cylinder block 31A of the engine 31, and the clutch case 52 is alsoconnected to the case main body 64A of the CVT case 64. With thisconfiguration, the clutch case 52 is sandwiched between the engine 31and the CVT case 64. The intake part 51 is formed in the clutch case 52,the cooling air inlet 64C is formed in the case main body 64A connectedto the clutch case 52, and the intake duct 67 for supplying the coolingair from the second air cleaner 46 is connected to the intake part 51.With this configuration, the cooling air flows from the intake part 51into the clutch case 52, and is sent from an inside of the clutch case52 through the cooling air inlet 64C to the inside of the CVT case 64,to thereby cool the inside of the CVT case 64. It should be noted thatthe intake part 51 may be formed in the case main body 64A.

The cooling air inlet 64C described above is formed in a regionsurrounding the output shaft 65A, and numeral intake fins 61C are formedin parts of the fixed sheave 61A of the driving pulley 61 facing thecooling air inlet 64C. In addition, in the movable sheave 62A and thefixed sheave 62B, numeral ribs 62D for reinforcement are formed whichmay function as exhaust fin.

As shown in FIGS. 8 and 9, the discharge part 64F is formed in acylindrical shape and extends rearward and slightly obliquely upwardfrom a rear upper part of the case main body 64A, and to the dischargepart 64F is connected an inflow opening 68X of an exhaust duct 68. Theexhaust duct 68 is bent at a base end part thereof so as to direct anexhaust direction downward, and has a bend 68A at an intermediate partso as to direct the exhaust direction inward of the vehicle body. Thebend 68A is provided with a narrow part 68B for reducing a dischargepathway of the cooling air (reducing a cross sectional area of thedischarge pathway). Further, an exhaust opening 68C in a terminal partof the exhaust duct 68 (downstream of the exhaust direction) iselongated in the longitudinal direction of the muffler 40 (transversedirection of the vehicle body) and the exhaust direction is orientedrearward of the vehicle body 3, so that the cooling air is dischargedtoward the gap between the muffler 40 and the heat shield plate 49 in adirection orthogonal to an extending direction of the muffler(longitudinal direction of the muffler 40). It should be noted that, asis apparent from FIG. 6, a cross-sectional horizontal length H2 of theexhaust opening 68C in the extending direction of the muffler is longerthan a cross-sectional horizontal length H1 of the inflow opening 68X inthe extending direction of the muffler, and a cross-sectional verticallength V2 of the exhaust opening 68C is shorter than a cross-sectionalvertical length V1 of the inflow opening 68X. Accordingly, thecross-sectional vertical length V2 of the exhaust opening 68C isapproximately half of the cross-sectional vertical length V1 of theinflow opening 68X, and the cross-sectional horizontal length H2 of theexhaust opening 68C is approximately twice the cross-sectionalhorizontal length H1 of the inflow opening 68X. To put it another way,roughly speaking, a cross sectional flow area of the exhaust opening 68Cis approximately the same as that of the inflow opening 68X, and thus across sectional configuration is adapted with which the cooling airflowing through the exhaust duct 68 is efficiently brought into contactwith a surface of the muffler 40.

Further, the exhaust duct 68 includes: an upper guide face 68D orientedrearward and downward for guiding the exhaust from the discharge part64F of the CVT case 64 to the narrow part 68B; a lower guide face 68Eoriented downward and frontward for downward guiding the exhaust fromthe narrow part 68B; and a distal end curved face 68F for guiding theexhaust from the narrow part 68B to the exhaust opening 68C. It shouldbe noted that the exhaust direction from the exhaust opening 68C to themuffler 40 is not necessarily be horizontal, as long as the direction isorthogonal to the longitudinal direction of the muffler 40. For example,the exhaust from the exhaust opening 68C may be blown obliquely upwardor obliquely downward toward the muffler 40. In addition, between theexhaust opening 68C and the ground perpendicularly below the exhaustopening 68C, a free space is provided, and thus the exhaust from theexhaust opening 68C can smoothly escape form inside the vehicle body 1,without being hindered by vehicle components.

With this configuration, along with driving rotation of the drivingpulley 61, a negative pressure is generated by the intake fins 61C, andambient air sucked into the second air cleaner 46 by this negativepressure is then sucked as the cooling air from the cooling air inlet64C through the intake duct 67 to the CVT case 64. The thus suckedcooling air flows from the driving pulley 61 to the driven pulley 62 inthe CVT case 64, and while flowing in this manner, the cooling air isbrought into contact with the driving pulley 61, the driven pulley 62and the endless belt 63 to remove heat therefrom and cool them.

The cooling air with which heat is removed from the inside of the CVTcase 64 then flows into the bulging part 64D formed in the case mainbody 64A, and along with an air flow caused by the rotation of thedriven pulley 62, the cooling air is discharged from the discharge part64F to an outside of the CVT case 64. In addition, when the cooling airis sent from the discharge part 64F to the exhaust duct 68, the flow issuppressed at the narrow part 68B, and thus an internal pressure of theCVT case 64 is increased. In this manner, by increasing the internalpressure of the CVT case 64, water, dust and the like can be preventedfrom entering a gap between the main flange face 64E of the case mainbody 64A and the sub flange face 64G of the cover member 64B. Then, thecooling air which has reached a terminal of the exhaust duct 68 issupplied from the exhaust opening 68C to the gap between the muffler 40and the heat shield plate 49, and heat can be released from the muffler40.

Effect of Embodiment

As described above, according to the present invention, the cooling airsupplied to the CVT case 64 is brought into contact with the drivingpulley 61, the driven pulley 62, and the endless belt 63, to therebycool them. In addition, since the cooling air is supplied from the casemain body 64A of the CVT case 64 and the cooling air is discharged fromthe discharge part 64F of the case main body 64A, even during anoperation of removing the cover member 64B, it is not necessary toremove a duct for supplying the cooling air, a duct for exhausting thecooling air and the like, and thus the operation is facilitated.

In the case main body 64A, the bulging part 64D bulging in a sideopposite to the cover member 64B (the transmission case 33 side) isformed, and the discharge part 64F is formed in the bulging part 64D. Inthe discharge part 64F, along with the rotation of the driven pulley 62,the wind pressure acting in a tangential direction from the upper partof the driven pulley 62 to the discharge part 64F can be acted on thecooling air, and the discharge is efficiently performed. In addition, arelatively large space away from the driven pulley 62 is secured in thebulging part 64D, and thus when the cooling air is discharged from thebulging part 64D to the discharge part 64F, the discharge can beefficiently performed without being blocked by the pulley and theendless belt. Moreover, when the cooling air is sent from the dischargepart 64F to the exhaust duct 68, by restricting the flow at the narrowpart 68B, the internal pressure of the CVT case 64 is increased, andthus water, dust and the like can be prevented from entering aconnecting interface between the case main body 64A and the cover member64B.

Further, the cooling air discharged from the exhaust opening 68C of theexhaust duct 68 is sent to a wide area along the longitudinal directionof the muffler 40. Furthermore, since the cooling air is dischargedrearward of the vehicle body 3 and supplied to the gap between themuffler 40 and the heat shield plate 49, the cooling air reaches thesurface of the muffler 40 without being influenced by the air flow fromoutside even when the vehicle body 3 is running, and thus the cooling ofthe muffler 40 can be excellently performed.

Especially, in the belt-type CVT 32, a strong tensile force tends to beexerted in the endless belt 63, which then acts on both the output shaft65A and the input shaft 33A, and thus on both the engine 31 and thetransmission case 33 in a direction that makes the output shaft 65A andthe input shaft 33A nonparallel. On the other hand, since the connectingplate 41 connects the upper part of the engine 31 and the upper part ofthe transmission case 33 in such a manner that the connecting plate 41is arranged in a posture that can firmly resist an action of the tensileforce, the relative position between the engine 31 and the transmissioncase 33 can be retained with high accuracy.

In addition, since the connecting plate 41 is disposed above the space30A between the engine 31 and the transmission case 33, water can beprevented from entering the electric components, such as the generator42 and the starter motor 43, arranged in the space below the connectingplate 41. Accordingly, when the vehicle body is washed with highpressure or when it rains hard, the problem of failure of the electriccomponents caused by water can be solved.

The cooling structure of the present invention is applicable not only tothe above-described work vehicle, but also to various types of vehicleshaving the engine and the belt-type CVT.

What is claimed is:
 1. A work vehicle having an engine and a belt-typeCVT, comprising: a muffler which is configured to flow exhaust from theengine and extends in a transverse direction of a vehicle body so as toallow the exhaust from the engine to flow in the transverse direction ofthe vehicle body; a CVT case which is configured to cover the belt-typeCVT and positioned frontward of the muffler in a longitudinal directionof the vehicle body, the CVT case including a cooling structureconfigured to introduce cooling air from outside, cool the belt-typeCVT, and discharge the cooling air from a discharge part; and an exhaustduct including: an inflow opening to be connected to the discharge partof the CVT case for allowing the cooling air to flow into the exhaustduct; and an exhaust opening for allowing the cooling air to flow outrearward of the vehicle body; wherein the exhaust opening is elongatedin an extending direction of the muffler and oriented in a directionthat allows the cooling air flowing out to hit the muffler; wherein across-sectional horizontal length of the exhaust opening in theextending direction of the muffler is longer than a cross-sectionalhorizontal length of the inflow opening, and a cross-sectional verticallength of the exhaust opening is shorter than a cross-sectional verticallength of the inflow opening.
 2. The work vehicle according to claim 1,wherein the cross-sectional horizontal length of the exhaust opening isapproximately twice the cross-sectional horizontal length of the inflowopening.
 3. The work vehicle according to claim 2, wherein a crosssectional flow area of the exhaust opening is approximately the same asa cross sectional flow area of the inflow opening.
 4. The work vehicleaccording to claim 1, wherein a heat shield plate is arranged along anouter face of the muffler at a distance, and the exhaust opening isoriented in a direction that allows the cooling air discharged from theexhaust duct to flow into a space between the muffler and the heatshield plate.
 5. The work vehicle according to claim 1, wherein theexhaust duct and the muffler are arranged at a position rearward of ashaft of a rear wheel in the longitudinal direction of the vehicle body.6. The work vehicle according to claim 1, wherein a free space isprovided between the exhaust opening and the ground perpendicularlybelow the exhaust opening.